My Sister's Killer
by Minds of a Criminal
Summary: The newest Agent shows up to work late only to announce that her sister was murdered. At a loss of what to do, her and the team try to track down the killer after being sent on a hunt, while she believes that she's next.
1. New Case

It was late it in the afternoon and the team at the BAU was sifting through files of the most recent cases. The doors to the agency were pushed open and in walked a young brunette with curly hair and grassy green eyes. Her black pencil skirt moved along with her body and her white blouse was loose on her upper torso. A red tie blew back past her along with her hair, her heels pushed against the ground quickly as she walked fast. People looked up, some had smiles on their faces, and others looked rather angry because of her terrible timing.

"Special Agent Mercer." Hotch stood up, his face cross with anger. "You're late." Mercer stopped in her step and turned to face him, tears rolling down her cheeks.

"My sister is dead."

Silence.

"Dead?" Morgan stood up from his seat as well as a few others. Mercer nodded.

"Somebody murdered her." She wiped tears away from her eyes.  
"How could somebody kill her, let alone allow you to walk away still alive...doesn't she live with you?" Reid questioned approaching the female.

"I don't know, but somebody killed her. I woke up this morning and..." She put her hand over her mouth, stifling the tears she didn't shed already.

"What's the deal guys?" Garcia's voice was heard over the static of the phone.

"Mercer's sister was murdered." JJ replied picking up the phone off of the desk it sat on.

"Ah, the old family first murderer." She answered almost in a happy tone. "Sorry for your loss." She added to make it sound more sympathetic.

"Thanks Garcia."

"Anytime my lovey." She answered.

* * *

"So your sister was murdered and the unsub did absolutely nothing to you?" Reid asked after everybody got situated in the conference room.

"Yes. But he must have done it while I was out last night." Mecer stood up and walked over to the whiteboard where she took the marker from Reid and began writing.

"Why last night?" Reid blinked and stepped away from the board.

"I was busy working and she was home alone. When I came home, I was so tired I didn't bother checking up on her. I just went to my room and crashed." Reid sat down.

"What next?" Mercer was writing on the board.

"I woke up and went to make breakfast. My frying pan was missing as well as a knife. I was getting sick of waiting for Emily so I went to her room and..." The female stopped writing on the board and stared at it instead.

"And she was dead." Prentiss finished her thought, arms crossed.

"Yes. But..." Mercer began again, pacing, her tears dried and no more were being shed.

"But what?" Morgan sat up. The female looked them all straight in the eye, one after another.

"I have no lead."

Everybody was quiet.

"No lead? Nothing?"

"No fingerprints, no sign of forced entry, nothing. The only thing I found was a note addressed to me." Mercer held up an envelope.

"Well read it!" Garcia boomed from the speakerphone. Mercer opened the envelope and unfolded the paper.

"You can't catch me. You won't catch me. I'm like a shadow; I'm not a shadow. The more you look for me, the more I begin to disappear. I'm your best friend, your greatest fear. It just makes no sense..."

"We can run it through the system and check the handwriting against other criminals that match this one's profile." Reid suggested. Mercer shook her head.

"It's written in my sister's handwriting. The unsub must have made her write it before she was killed." She threw it down on the table and pulled at her hair, furiously.

"Calm down. I understand your mental conditions aren't well, plus the fact you're going through the grieving process which deals with high levels of sadness, anger, depression, regret, disbelief and can lead to psychotic behaviors. Right now, you need to stay stress free. No anxiety attacks, no naps, no late nights, no talking to the little voices inside your head..." The doctor reassured the female as she took a deep breath and nodded.

"I just...there's nothing. This case is going to fall through the cracks, but I can't give up on Emily..."

"Is the body still at your house?"

"Yes. My parents are having it taken away to be cremated in a couple of days, though. They wouldn't let them touch Em's poor body. I can't believe they didn't start a World War over it..."

"Then we need to search the crime scene again until they take it away..."

* * *

"There's nothing here. Really. " Mercer wiped her hands with a dish towel. "I'm PART of your team. I should know what to do..." She murmured and stood in the doorway of the bedroom. Sure enough, her sister's body was lying on the floor, covered with a thick sheet. She cringed once her eyes trailed over to the body, and she turned her head away.

"Well you may have missed something..." Prentiss opened a drawer and searched through it.

"Be careful. I want to keep some of her stuff for memories..." The young girl blurted out and Prentiss looked at her for a long moment. "Take what you need as evidence, but I want to remember my sister..."

A couple seconds later, Little Annie's phone blasted a familiar ringtone_._

"Talk to me Garcia." She turned her back to her team, embarrassed.

"You should change your ringtone sweetheart~" Garcia hummed and clicked away at her keyboard.

"What do you have for me, Garcia?" Mercer answered a little impatiently.

"Cool your hot little head...I've searched for break ins, murders with knives-"

"She wasn't killed with a knife." Reid stood up and took the Droid X from Mercer's hand, putting it on speaker.

"What do you mean...? It's right there on the floor covered in her blood."

"As true as that is, she was killed by the blood trauma from her head wounds. The frying pan method was obviously to knock her down onto the floor where the unsub decided to bash her head into something...the knife was stabbed into her arms, legs, and upper body but it wasn't the cause of death...she also seems to have unexplainable marks on her cheeks and other places of her body. They almost look like bite marks. Can you get anything from that, Garcia?"

"Sugar I can do anything. I'm better than Superman, after all." She grinned and tapped away at the keys. "Let's see...I've narrowed down the list to break ins, murders, knives, head wounds..."

"Add serial killer to the list."

"Done and done~ Sending it your way." The line was disconnected and Reid handed Mercer back her phone. She snatched it and put it back into her pocket, flipping the light switch on.

"Yuck...everything looks nastier in the light." She made a face and stepped over her sister's body. "Reid, let me see those photos." She held her hand out, expecting him to hand them over. He did, but she wasn't paying attention and they all fell onto the floor, scattered everywhere in the room.

"Now you have to clean them up..." He stared at them, and then looked over at Mercer. Her grass stained eyes were focused on something under the bed. It was white, and looked like a piece of paper.

She took it and stood up, opening the envelope, and then pulling out a piece of paper, folded very neatly. Unfolding the paper, Mercer read it and blinked.

"What?" Prentiss got closer to Mercer.

"He's sending us on a scavenger hunt..." She handed over the paper and left the room, escaping into the kitchen.

"What's it say, Prentiss?"

She was silent.

"Coffee shop." She replied hoarsely, and handed it to Hotch.

"She's right. Nothing else on it."

"The killer may be retracing the steps he took, trying to put us in his exact shoes...but this could mean he's leading us into a trap if these are the places he visited yesterday." Reid picked up the last of the photos and put them away in the file.

"You're right...but we have our lead." The rest of the team left the room and joined Annie who was leaning over the sink.

"Something wrong?" Morgan put his hand on her shoulder.

"My sister was at the coffee shop yesterday morning. She goes there every day."


	2. Coffee Shop

"So is it possible the unsub knew your sister?" Reid looked at Mercer who sat beside him in the backseat of the car.  
"Em never brought over anybody...maybe she was afraid that I would embarrass her or that I wouldn't approve, but she never mentioned she was seeing anyone." Mercer turned her head to look at him for a long minute in silence, then turned her head to look out the window.  
"Maybe he's a stalker." Morgan suggested from the driver's seat.

"A stalker? Stalker's don't kill, they stalk...right?"  
"Not necessarily. See, a stalker is wrapped around the idea that one certain person, or multiple people, did something to him or her, or that the person is theirs or meant to be with them for life. Stalkers try to get with the person as much as they can without being spotted which explains the distance they follow the person from. Now, if a stalker is in love with the person they are stalking, they'll feel threatened if they're seen with somebody else, and might decide to attack their stalkee, be it rape, murder, kidnapping, or a simple physical assault. If they can't have them, nobody can." Reid pulled out the file once more. "Your sister was killed and the work seemed to be played out very well."

Annie moved closer so she could see the photographs.  
"What do you mean?"

"See how she was positioned? She looks almost as if she was attacked in her sleep-"  
"Because she probably was!" Mercer narrowed her eyes. "My sister never stays up late."  
"Maybe she finally discovered she can get away with things when you weren't around." Prentiss glanced at her.

"She's not that type of person...I know my sister better than that." She took a deep breath. "The coffee shop is just around the corner..." Annie hung her head between her knees, angry with herself. Reid patted her head gently and returned to looking at the photos, trying to make something out of it.

"This is the place?" Morgan stopped in front of the small café and turned the car off.

"Ya, it is...but what are we even looking for?" The brunette opened the door and climbed out, shutting it behind her. The second car parked beside theirs, and the rest of the team followed her into the coffee shop.

It looked like a normal, little, café where anybody would go. It was empty on this particular day, and that was good news.

"Good Morning, Little Annie." The man from behind the counter smiled.

"Morning Joey." She moved closer to the counter and leaned over it. "Anything good?"  
"Nya, but I heard there's been a lot of break ins lately. And somebody was murdered." He looked at her in disbelief and wiped up the counter.

"That was probably my sister..." She walked away from the counter and began looking around. "Mind if we search the place?"  
Joey ran a hand through his dirty blonde hair and shook his head and hesitated. "Not at all."  
"Good. Morgan, Prentiss, check the back room. Hotch, Rossi, around back. Reid, check the tables, couches, bookshelf, everything." Annie jumped over the counter and began going through everything she could.

* * *

In the back room, Morgan went through any boxes he could and Prentiss opened the cabinets and drawers.

"Nothing suspicious..." She muttered and dusted off the shelf to get a better look. Morgan opened a box and stared. "Prentiss come here." She stepped over the fallen objects and joined Morgan.

"It's a shirt with blood on it..." She looked at him. "Do you think it's Emily's blood?"  
"We won't know until we test the DNA. Keep looking. There may be something else here."

* * *

"These books are old...does anybody read them?" Reid flipped through a book with a poor spine and wrinkled pages. Joey shook his head.

"Nobody reads books here. There just for show." He shrugged. Mercer hopped back over the counter.  
"Nothing." She put her hands on her hips and stomped her foot against the floor, trying to break the heel of her shoe. Reid put the book away and quickly made his way to the girl, putting his foot on top of hers.

"Deep breaths." He reminded her, waiting. She sighed and took a deep breath, then released it. "Happy?"  
"Very." He released her foot and went back to looking through the bookshelf. Dusting off her foot, she joined him at the shelf and began pulling out books, flipping through them, and then throwing them behind her.

"Heeey. Those are considered antiques dating back to the-"  
"I don't care we're looking for clues." She reminded him and snatched the book out of his hand and flipped through it. Before she went to throw it behind her, she noticed something.

"Is this book part of a set?"

* * *

Out back there was nothing but a pond and seats for people to sit outside and drink or eat.

"It looks normal to me." Rossi mumbled and looked through the bushes that surrounded the small area. Something caught Hotch's eye.

"In the water." He pointed to a reflective object sitting in the muck of the shallow end. He rolled his sleeve up and grabbed it, shaking extra water and mud away.  
"It's a bracelet."  
"Emily's bracelet?"

* * *

"We found a shirt with blood stains on it. We believe it may be Emily's blood." Morgan and Prentiss rejoined Reid and Mercer in the main room of the café.

"And we found a bracelet in the water. Did Emily wear a bracelet?" Rossi handed it over to Annie who was still busy with the book. She looked up and took the bracelet.

"Ya, this is Em's. She wore it all the time. Lucky bracelet, I think she said it was..." She frowned and slowly handed it back, flipping through the thin book. A large letter G was written in black, permanent marker. Her eyes got bigger.

"How many more books are in this set?" She asked Reid quickly, her volume getting higher.

"Uh, twelve I believe..." Mercer put the book down; keeping the page opened and took the second volume. She flipped through that book until she found another letter. R.

"Guys grab a book. Tell me what letter you find!" She put that one down and began pacing, staying close to the window. While she did so, the rest of the team began going through the books.

"Found an S."  
"I got an O."

"C over here."

"E."  
"This one has a Y."

"Keep looking!" She spun around, her face flushed with anger. Reid stepped forward a bit and Mercer took a deep breath right away and he continued through the books.

* * *

Her green eyes observed the glass as carefully as they could. Something had to be wrong with it, but she found nothing.

"Nobody broke the windows..." She went over to the door and opened it. "No sign of forced entry...Joey, are there any more doors that are used to get into the store?" She looked at her team and watched them sift through book pages.

"Um...ya...the back door." He pointed in the direction of the door. She nodded and walked that way, finally getting to the door. She was surprised it could be opened both ways, but she wasn't surprised when she found scuff marks on the side.  
"He broke in through the back door." She announced, her heels clicking against the marble finish of the shop.

"Forced entry, I assume." Reid was now rearranging the books so that the letters made sense.

"Yep."  
"Wait, somebody broke in!" Joey panicked.

"It's okay. Nothing was stolen. But the unsub did vandalize the books which means we can arrest him for vandalizing public property, if nothing more." She told him, and sat down in a chair, staring at the books. "For somebody with an IQ of 187 or something, you're having a hard time with letters..." Reid looked up, looking a little frustrated with her.

"_Grocery Store"_ a voice echoed in her head.

"Grocery Store..." She whispered and smacked Reid's hands away, turning the books and putting them in the correct order.

"How'd you do that...?" Morgan raised an eyebrow.

"If your family members have it you're more likely to get the disease yourself..." She mused to herself quietly.

"What? You really need to speak up..." Prentiss looked at her.

"_You're right, you know."_ The voice echoed once more before disappearing. Mercer looked up.  
"Nothing." She replied, swallowing. "But that's where we're going next. Grocery store." She stood up and pulled out her phone, dialing it.

Using her pen, Garcia hit the button, smiling.

"I'm here all day and all night just for you~" She answered.

"Garcia, I need you to do another check." She told her while leaving the coffee shop followed by her team.

"Anything for my babies."

"Check for anybody who's committed a break in, murder, known for using knives and bashing their victims heads, and leaving any sort of clue or note, like you'd find in ransom letters."

"Okay I've gooot...twenty-three suspects up, all of which sound like your profile."

"Good, now can you check within this area specifically the area I live in?"

"Now it's...fourteen." She answered. Mercer stared at the coffee shop sign, while the others got into the cars.

"Throw serial killer into the mix." She finally said.

"Brings it down to eight. Sending it all your way. Garcia over and out~" Mercer got back into the car and shut the door.

"Let's get back to the BAU and run a test and the shirt and blood, then we'll take it from there." Morgan announced after pulling out of the small parking lot.

"Sounds good." Prentiss looked back at the two younger agents in the back seat.

Both of them nodded and Mercer closed her eyes, hoping she'd get a nice nap on the way back.

Instead, she found herself dreaming about her sister, and her sister's murderer.

She was standing in the doorway of the bedroom and the figure was dressed in black as they folded her arms over her chest, to make it appear that she would rest in peace.

"Turn around!" Mercer had her gun out, ready to shoot. The figure stood up and turned to look at her, but it was too dark to see. "Let me see your face." Her hands were shaking, and she swallowed, trying to still appear as the tougher person. The figure pulled a gun out of their pocket, and Mercer pulled the trigger.

There was no ammo in the gun. She dropped it and stumbled backwards.

The figure laughed and shot her in her right side...

* * *

Mercer woke up clutching her side in pain.

"What's wrong?" Reid looked at her, and Prentiss couldn't help but look back at her as well.

"Nothing..." She kept her hands over her side, where she had been shot a week earlier while trying to handle a hostage situation. It still hurt, it always would. Maybe not physical pain, but the mental pain never went away.

The car stopped and everybody exited the vehicles and went right into the building. Mercer stopped in front of the elevator and heard screaming in her head. It was the screaming of a little girl.

She closed her eyes and opened them, then joined the rest of the team in the elevator,

"You really don't seem like yourself." Reid told the girl point blank.

"Grieving process." She replied, lying through her teeth.

_Bing!_

The doors of the elevator opened and the first one out was Mercer.

"We need to run a test on the blood on this shirt." She pushed the doors to the BAU opened and looked around at the faces that turned to look at her and the team that she left in the dust.

"Ya...lab test." Prentiss repeated, still staring at the brunette.

* * *

She was already inside the lab, and everything was ready. Annie Mercer was pacing and twirling her hair with her index finger.

"I told you to calm down before. Now's not the time for an Anxiety attack, even though it may feel like it."  
"I know, you're right. But...I'm so nervous, and scared..." She repeated and misplaced her foot, nearly falling onto the floor before catching herself on the strap of Reid's messenger bag. "Damn heels." She returned to pacing.

"Well, we have your test done." The woman in charge of the process returned back to the group, causing Mercer's pacing to cease.  
"Well?" She asked frantically.

"It's Emily Mercer's blood."


End file.
